Apparatus, method, system, program and recording medium related to beamforming

ABSTRACT

[Solution] A first apparatus of the present invention includes: a first communication processing unit configured to transmit reference signals using beamforming; and a second communication processing unit configured to receive a handover message from a source base station of a handover of a terminal apparatus. The handover message includes beam related information related to a beam. The first communication processing unit is configured to receive an access signal of the terminal apparatus based on the beam related information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. application Ser.No. 16/321,749, filed on Jan. 29, 2019, which is a National Stage ofInternational Application No. PCT/JP2017/024584 filed Jul. 5, 2017,claiming priority based on Japanese Patent Application No. 2016-152618filed Aug. 3, 2016, the disclosure of which is incorporated herein inits entirety by reference.

BACKGROUND Technical Field

The present invention relates to an apparatus, a method, a system, aprogram, and a recording medium related to beamforming.

Background Art

In order to achieve a drastic increase in the capacity of mobilenetworks, not only currently used frequency bands such as a severalhundred megahertz band and a several gigahertz band but also a higherfrequency band such as a several ten gigahertz band may be used. Inparticular, in the Fifth Generation (5G), in order to make the most useof such a band, studies are made on transferring signals to users byforming narrow directional beams using a large number of antennas.

In a higher frequency band, in order to compensate a large propagationloss, it is conceivable to use beamforming for the transmission of notonly system information and paging information but also all of downlinksignals/downlink channels including common pilot signals, referencesignals or the like. Similarly, as for uplink, in order to compensate apropagation loss, it is also conceivable to use beamforming for thereception of all uplink signals/uplink channels.

For example, PTL 1 discloses an art in which a downlink beam ID and anuplink beam ID are included in a HANDOVER REQUEST message transmitted toa target base station from a source base station of a handover of aterminal apparatus. Further, according to PTL 1, the downlink beam ID isused for designating a downlink beam for transmitting data to theterminal apparatus after the handover, and the uplink beam ID is usedfor designating an uplink beam for receiving data from the terminalapparatus after the handover. This makes it possible to omit anoperation for selecting beams at the time of the handover, leading to areduction in delay of the handover.

CITATION LIST Patent Literature

[PTL 1] JP2014-531852T

SUMMARY Technical Problem

According to the art disclosed in PTL 1, however, a propagation loss iscompensated in the transmission/reception of data after the handover,but a propagation loss is not compensated in the transmission/receptionof control signals between the terminal apparatus and the target basestation in the handover. In particular, it may not be possible for thetarget base station to receive an access signal (for example, an uplinksignal in random access) of the terminal apparatus due to a largepropagation loss. This, as a result, leads to a possibility of anincreased failure rate of the handover.

It is an example object of the present invention to make it possible toincrease a possibility of a success of a handover.

Solution to Problem

A first apparatus according to an example aspect of the presentinvention includes: a first communication processing unit configured totransmit reference signals using beamforming; and a second communicationprocessing unit configured to receive a handover message from a sourcebase station of a handover of a terminal apparatus. The handover messageincludes beam related information related to a beam. The firstcommunication processing unit is configured to receive an access signalof the terminal apparatus based on the beam related information.

A second apparatus according to an example aspect of the presentinvention includes: a first communication processing unit configured toreceive, from a terminal apparatus, first beam related informationrelated to a beam, the first beam related information being informationfor a base station which transmits reference signals using beamforming;and a second communication processing unit configured to transmit, tothe base station, a handover message including second beam relatedinformation corresponding to the first beam related information. Thesecond beam related information is information to be used by the basestation to receive an access signal of the terminal apparatus.

A third apparatus according to an example aspect of the presentinvention includes; a reception processing unit configured to receivereference signals transmitted by a first base station using beamforming;and a transmission processing unit configured to transmit, to a secondbase station, first beam related information related to a beam, thefirst beam related information being information for the first basestation. The first beam related information corresponds to second beamrelated information to be used by the first base station to receive anaccess signal.

A first method according to an example aspect of the present inventionincludes: transmitting reference signals using beamforming; receiving ahandover message from a source base station of a handover of a terminalapparatus, the handover message including beam related informationrelated to a bean and receiving an access signal of the terminalapparatus based on the beam related information.

A second method according to an example aspect of the present inventionincludes: receiving, from a terminal apparatus, first beam relatedinformation related to a beam, the first beam related information beinginformation for a base station which transmits reference signals usingbeamforming; and transmitting, to the base station, a handover messageincluding second beam related information corresponding to the firstbeam related information. The second beam related information isinformation to be used by the base station to receive an access signalof the terminal apparatus.

A third method according to an example aspect of the present inventionincludes: receiving reference signals transmitted by a first basestation using beamforming; and transmitting, to a second base station,first beam related information related to a beam, the first beam relatedinformation being information for the first base station. The first beamrelated information corresponds to second beam related information to beused by the first base station to receive an access signal.

A system according to an example aspect of the present inventionincludes: a first base station, a second base station, and a terminalapparatus. The first base station is configured to transmit referencesignals using beamforming. The terminal apparatus is configured toreceive the reference signals, and transmit, to the second base station,first beam related information related to a beam, the first beam relatedinformation being information for the first base station. The secondbase station is configured to transmit, to the first base station, ahandover message including second beam related information correspondingto the first beam related information. The first base station isconfigured to receive an access signal of the terminal apparatus basedon the second beam related information.

A first program according to an example aspect of the present inventionis a program for causing a processor to execute; transmitting referencesignals using beamforming; receiving a handover message from a sourcebase station of a handover of a terminal apparatus, the handover messageincluding beam related information related to a beam; and receiving anaccess signal of the terminal apparatus based on the beam relatedinformation.

A second program according to an example aspect of the present inventionis a program for causing a processor to execute: receiving, from aterminal apparatus, first beam related information related to a beam,the first beam related information being information for a base stationwhich transmits reference signals using beamforming; and transmitting,to the base station, a handover message including second beam relatedinformation corresponding to the first beam related information. Thesecond beam related information is information to be used by the basestation to receive an access signal of the terminal apparatus.

A third program according to an example aspect of the present inventionis a program for causing a processor to execute: receiving referencesignals transmitted by a first base station using beamforming; andtransmitting, to a second base station, first beam related informationrelated to a beam, the first beam related information being informationfor the first base station. The first beam related informationcorresponds to second beam related information to be used by the firstbase station to receive an access signal.

A first recording medium according to an example aspect of the presentinvention is a computer-readable non-transitory recording medium havingrecorded thereon a program for causing a processor to execute:transmitting reference signals using beamforming; receiving a handovermessage from a source base station of a handover of a terminalapparatus, the handover message including beam related informationrelated to a beam; and receiving an access signal of the terminalapparatus based on the beam related information.

A second recording medium according to an example aspect of the presentinvention is a computer-readable non-transitory recording medium havingrecorded thereon a program for causing a processor to execute:receiving, from a terminal apparatus, first beam related informationrelated to a beam, the first beam related information being informationfor a base station which transmits reference signals using beamforming;and transmitting, to the base station, a handover message includingsecond beam related information corresponding to the first beam relatedinformation. The second beam related information is information to beused by the base station to receive an access signal of the terminalapparatus.

A third recording medium according to an example aspect of the presentinvention is a computer-readable non-transitory recording medium havingrecorded thereon a program for causing a processor to execute: receivingreference signals transmitted by a first base station using beamforming;and transmitting, to a second base station, first beam relatedinformation related to a beam, the first beam related information beinginformation for the first base station. The first beam relatedinformation corresponds to second beam related information to be used bythe first base station to receive an access signal.

Advantageous Effects of Invention

According to an example aspect the present invention, it is possible toincrease a possibility of a success of a handover. Note that the presentinvention may provide other effects in place of or together with theabove effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram illustrating an example of theschematic configuration of a system according to a first exampleembodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of the schematicconfiguration of a first base station according to the first exampleembodiment.

FIG. 3 is a block diagram illustrating an example of the schematicconfiguration of a second base station of the first example embodiment.

FIG. 4 is a block diagram illustrating an example of the schematicconfiguration of a terminal apparatus of the first example embodiment.

FIG. 5 is an explanatory diagram for explaining an example of aplurality of beams by which reference signals are transmitted.

FIG. 6 is an explanatory diagram for explaining an example of radioresources (time resources) to be used for transmitting the referencesignals.

FIG. 7 is an explanatory diagram for explaining an example of ameasurement report of the terminal apparatus.

FIG. 8 is a sequence diagram for explaining an example of a schematicflow of processing according to the first example embodiment.

FIG. 9 is an explanatory diagram for explaining an example of radioresources indicated by resource information.

FIG. 10 is a sequence diagram for explaining an example of a schematicflow of processing of a first example alteration of the first exampleembodiment.

FIG. 11 is a sequence diagram for explaining a schematic flow ofprocessing of a second example alteration of the first exampleembodiment.

FIG. 12 is an explanatory diagram illustrating an example of theschematic configuration of a system according to a second exampleembodiment.

FIG. 13 is a block diagram illustrating an example of the schematicconfiguration of a first base station of the second example embodiment.

FIG. 14 is a block diagram illustrating an example of the schematicconfiguration of a second base station of the second example embodiment.

FIG. 15 is a block diagram illustrating an example of the schematicconfiguration of a terminal apparatus of the second example embodiment.

FIG. 16 is a sequence diagram for explaining an example of a schematicflow of processing of the second example embodiment.

DESCRIPTION OF THE EXAMPLE EMBODIMENTS

Hereinafter, example embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Notethat, in the specification and the drawings, elements whose descriptionscan be the same may be denoted by the same reference signs, therebyomitting overlapping descriptions.

The description will be given in the following order.

1. Outline of Example Embodiments of Present Invention

2. First Example Embodiment

2.1. Configuration of System

2.2. Configuration of Base Station 100

2.3. Configuration of Base Station 200

2.4. Configuration of Terminal Apparatus 300

2.5. Technical Features

2.6. Example alterations

3. Second Example Embodiment

3.1. Configuration of System

3.2. Configuration of Base Station 500

3.3. Configuration of Base Station 600

3.4. Configuration of Terminal Apparatus 700

3.5. Technical Features

1. Outline of Example Embodiments of Present Invention

The outline of the example embodiments of the present invention will bedescribed first.

(1) Technical Problem

In order to achieve a drastic increase in the capacity of mobilenetworks, not only currently used frequency bands such as a severalhundred megahertz band and a several gigahertz band but also a higherfrequency band such as a several ten gigahertz band may be used. Inparticular, in the Fifth Generation (5G), in order to make the most useof such a band, studies are made on transferring signals to users byforming narrow directional beams using a large number of antennas.

In a higher frequency band, in order to compensate a large propagationloss, it is conceivable to use beamforming for the transmission of notonly system information and paging information but also all of downlinksignals/downlink channels including common pilot signals, referencesignals or the like. Similarly, as for uplink, in order to compensate apropagation loss, it is also conceivable to use beamforming for thereception of all uplink signals/uplink channels.

For example, patent literature (JP2014-531852T) discloses an art inwhich a downlink beam ID and an uplink beam ID are included in aHANDOVER REQUEST message transmitted to a target base station from asource base station of a handover of a terminal apparatus. Further,according to the patent literature, the downlink beam ID is used fordesignating a downlink beam for transmitting data to the terminalapparatus after the handover, and the uplink beam ID is used fordesignating an uplink beam for receiving data from the terminalapparatus after the handover. This makes it possible to omit anoperation for selecting beams at the time of the handover, leading to areduction in delay of the handover.

According to the art disclosed in the patent literature, however, apropagation loss is compensated in the transmission/reception of dataafter the handover, but a propagation loss is not compensated in thetransmission/reception of control signals between the terminal apparatusand the target base station in the handover. In particular, it may notbe possible for the target base station to receive an access signal (forexample, an uplink signal in random access) of the terminal apparatusdue to a large propagation loss. This, as a result, leads to apossibility of an increased failure rate of the handover.

Therefore, it is desirable to make it possible to increase a possibilityof a success of the handover.

(2) Technical Features

In the example embodiments of the present invention, for example, afirst base station (base station located around a terminal apparatus)transmits reference signals using beamforming, and the terminalapparatus performs the measurements of the reference signals. Further,the terminal apparatus transmits first beam related information for thefirst base station (and measurement results) to a second base station(serving base station of the terminal apparatus). For example, the firstbeam related information indicates one of a plurality of sets ofbeamforming weights (for example, a preferred beamforming weight).

Thereafter, a handover of the terminal apparatus from the second basestation (source base station) to the first base station (target basestation) is performed. In this case, the second base station (sourcebase station) transmits, to the first base station (target basestation), a handover message (for example, a HANDOVER REQUEST message)including second beam related information (for example, the sameinformation as the first beam related information) corresponding to thefirst beam related information.

In particular, in the example embodiments of the present invention, thefirst base station receives an access signal of the terminal apparatusbased on the second beam related information. For example, the firstbase station receives the access signal using the preferred beamformingweight.

This makes it possible to, for example, compensate a propagation loss ofthe access signal. Accordingly, it is possible to increase a possibilityof a success of the handover.

Note that the above technical features are specific examples of theexample embodiments of the present invention, and as a matter of course,the example embodiments of the present invention are not limited to theabove technical features.

2. First Example Embodiment

Next, a first example embodiment of the present invention will bedescribed with reference to FIG. 1 to FIG. 11.

<2.1. Configuration of System>

An example of the configuration of a system 1 according to the firstexample embodiment will be described with reference to FIG. 1. FIG. 1 isan explanatory diagram illustrating an example of the schematicconfiguration of the system 1 according to the first example embodiment.Referring to FIG. 1, the system 1 includes a base station 100, a basestation 200, and a terminal apparatus 300.

For example, the system 1 may be a system conforming to the standard of3GPP (Third Generation Partnership Project). More specifically, thesystem 1 may be a system conforming to the standard of the FifthGeneration (5G), for instance.

(1) Base Station 100

The base station 100 performs radio communication with terminalapparatuses located in a cell 10 (or a coverage area 10). In the firstexample embodiment, the base station 100 uses beamforming for the radiocommunication.

In particular, in the first example embodiment, the base station 100transmits reference signals (RS) using the beamforming. The referencesignal is a signal for the measurements of received signal strengthand/or received quality and corresponds to, for example, CRS(Cell-specific Reference Signal) or CSI-RS (Channel State InformationReference Signal) in LTE (Long Term Evolution). The reference signal maybe called CRS or CSI-RS as in LTE, or may be called differently (forexample, “an XXX reference signal” (XXX is an arbitrary term), “a pilotsignal”, or a completely different another signal name). The basestation 100 may transmit all kinds of reference signals (for example,CRS, CSI-RS, a UE-specific RS, and/or MBSFN (Multicast/Broadcast over aSignal Frequency Network) RS) using the beamforming. Alternatively, thebase station 100 may transmit partial kinds of the reference signalsusing the beamforming without transmitting the other kinds of referencesignals using the beamforming.

The base station 100 may transmit not only data and the referencesignals but also other downlink signals/downlink channels (for example,all signals/channels) using the beamforming.

Note that the base station 100 is anode that performs radiocommunication with the terminal apparatuses, in other words, is a nodeof RAN (Radio Access Network). For example, the base station 100 may beNodeB, H-NodeB (Home Node B), eNodeB (evolved Node B), or H-eNodeB (Homeevolved Node B), or may be gNodeB (generation Node B) in 5G The basestation 100 may include a plurality of units (or a plurality of nodes).The plurality of units (or the plurality of nodes) may include a firstunit (or a first node) which processes lower protocol layers and asecond unit (or a second node) which processes higher protocol layers.As one example, the first unit may be called DU (Distributed Unit) or AU(Access Unit), and the second unit may be called CU (Center/CentralUnit). As another example, the first unit may be called RU (Radio Unit)or RU (Remote Unit), and the second unit may be called DU (DigitalUnit). The RU may be RRH (Remote Radio Head) or RRU (Remote Radio Unit),and the DU may be BBU (Base Band Unit). As a matter of course, the namesof the first unit (or the first node) and the second unit (or the secondname) are not limited to these examples. Alternatively, the base station100 may be a single unit (or a single node). In this case, the basestation 100 may be one of the aforesaid plurality of units (for example,one of the first unit and the second unit), or may be connected toanother unit out of the plurality of units (for example, the other ofthe first unit and the second unit).

(2) Base Station 200

The base station 200 performs radio communication with terminalapparatuses located in a cell 20 (or a coverage area 20).

In the first example embodiment, for example, the base station 200performs radio communication with the terminal apparatuses usingbeamforming similarly to the base station 100. Alternatively, the basestation 200 may perform radio communication with the terminalapparatuses using the beamforming in a manner different from that of thebase station 100, or may perform radio communication with the terminalapparatuses not using the beamforming.

Note that the base station 200 is also a node that performs radiocommunication with the terminal apparatuses, in other words, it is anode of RAN, similarly to the base station 100.

(3) Terminal Apparatus 300

The terminal apparatus 30 performs radio communication with basestations. For example, the terminal apparatus 300 performs radiocommunication with the base station 100 when located in the cell 10, andperforms radio communication with the base station 200 when located inthe cell 20.

In particular, in the first example embodiment, a handover of theterminal apparatus 300 from the base station 200 to the base station 100is performed (due to, for example, the movement of the terminalapparatus 300). In this case, the base station 200 is a source basestation of the handover, and the base station 100 is a target basestation of the handover.

<2.2. Configuration of Base Station 100>

Next, an example of the configuration of the base station 100 of thefirst example embodiment will be described with reference to FIG. 2.FIG. 2 is a block diagram illustrating an example of the schematicconfiguration of the base station 100 of the first example embodiment.Referring to FIG. 2, the base station 100 includes a radio communicationunit 110, a network communication unit 120, a storage unit 130, and aprocessing unit 140.

(1) Radio Communication Unit 110

The radio communication unit 110 wirelessly transmits/receives signals.For example, the radio communication unit 110 receives signals fromterminal apparatuses and transmits signals to terminal apparatuses.

(2) Network Communication Unit 120

The network communication unit 120 receives signals from a backhaul andtransmits signals to the backhaul.

(3) Storage Unit 130

The storage unit 130 temporarily or permanently stores programs andparameters for the operation of the base station 100 and various data.

(4) Processing Unit 140

The processing unit 140 provides various functions of the base station100. The processing unit 140 includes a first communication processingunit 141 and a second communication processing unit 143. Note that theprocessing unit 140 can further include other constituent elementsbesides these constituent elements. That is, the processing unit 140 canperform operations other than the operations of these constituentelements. Specific operations of the first communication processing unit141 and the second communication processing unit 143 will be describedin detail later.

For example, the processing unit 140 (first communication processingunit 141) communicates with terminal apparatuses (for example, theterminal apparatus 300) via the radio communication unit 110. Forexample, the processing unit 140 (second communication processing unit143) communicates with other network nodes (for example, the basestation 200) via the network communication unit 120.

(5) Implementation Example

The radio communication unit 110 may be implemented by an antenna, a RF(Radio Frequency) circuit, or the like, and the antenna may be adirectional antenna. The network communication processing unit 120 maybe implemented by a network adapter, a network interface card, or thelike. The storage unit 130 may be implemented by a memory (for example,a nonvolatile memory and/or a volatile memory) and/or a hard disk or thelike. The processing unit 140 may be implemented by a BB (Baseband)processor and/or another processor. The first communication processingunit 141 and the second communication processing unit 143 may beimplemented by the same processor, or may be implemented separately bydifferent processors. The aforesaid memory (storage unit 130) may beincluded in such a processor (chip).

The base station 100 may include a memory which stores a program and oneor more processors capable of executing the program. The one or moreprocessors may perform the operation of the processing unit 140 (thefirst communication processing unit 141 and the second communicationprocessing unit 143). The program may be a program for causing the oneor more processors to execute the operation of the processing unit 140(the first communication processing unit 141 and the secondcommunication processing unit 143).

<2.3. Configuration of Base Station 200>

Next, an example of the configuration of the base station 200 of thefirst example embodiment will be described with reference to FIG. 3.FIG. 3 is a block diagram illustrating an example of the schematicconfiguration of the base station 200 of the first example embodiment.Referring to FIG. 3, the base station 200 includes a radio communicationunit 210, a network communication unit 220, a storage unit 230, and aprocessing unit 240.

(1) Radio Communication Unit 210

The radio communication unit 210 wirelessly transmits/receives signals.For example, the radio communication unit 210 receives signals fromterminal apparatuses and transmits signals to terminal apparatuses.

(2) Network Communication Unit 220

The network communication unit 220 receives signals from a backhaul andtransmits signals to the backhaul.

(3) Storage Unit 230

The storage unit 230 temporarily or permanently stores programs andparameters for the operation of the base station 200 and various data.

(4) Processing Unit 240

The processing unit 240 provides various functions of the base station200. The processing unit 240 includes a first communication processingunit 241 and a second communication processing unit 243. Note that theprocessing unit 240 can further include other constituent elementsbesides these constituent elements. That is, the processing unit 240 canperform operations other than the operations of these constituentelements. Specific operations of the first communication processing unit241 and the second communication processing unit 243 will be describedin detail later.

For example, the processing unit 240 (first communication processingunit 241) communicates with terminal apparatuses (for example, theterminal apparatus 300) via the radio communication unit 210. Forexample, the processing unit 240 (second communication processing unit243) communicates with other network nodes (for example, the basestation 100) via the network communication unit 220.

(5) Implementation Example

The radio communication unit 210 may be implemented by an antenna, aradio frequency (RF) circuit, or the like, and the antenna may be adirectional antenna. The network communication unit 220 may beimplemented by a network adapter, a network interface card, or the like.The storage unit 230 may be implemented by a memory (for example, anonvolatile memory and/or a volatile memory) and/or a hard disk or thelike. The processing unit 240 may be implemented by a baseband (BB)processor and/or another processor. The first communication processingunit 241 and the second communication processing unit 243 may beimplemented by the same processor, or may be implemented separately bydifferent processors. The aforesaid memory (storage unit 230) may beincluded in such a processor (chip).

The base station 200 may include a memory which stores a program and oneor more processors capable of executing the program. The one or moreprocessors may perform the operation of the processing unit 240 (thefirst communication processing unit 241 and the second communicationprocessing unit 243). The program may be a program for causing the oneor more processors to execute the operation of the processing unit 240(the first communication processing unit 241 and the secondcommunication processing unit 243).

<2.4. Configuration of Terminal Apparatus 300>

Next, an example of the configuration of the terminal apparatus 300 ofthe first example embodiment will be described with reference to FIG. 4.FIG. 4 is a block diagram illustrating an example of the schematicconfiguration of the terminal apparatus 300 of the first exampleembodiment. Referring to FIG. 4, the terminal apparatus 300 includes aradio communication unit 310, a storage unit 320, and a processing unit330.

(1) Radio Communication Unit 310

The radio communication unit 310 wirelessly transmits/receives signals.For example, the radio communication unit 310 receives signals from basestations and transmits signals to base stations.

(2) Storage Unit 320

The storage unit 320 temporarily or permanently stores programs andparameters for the operation of the terminal apparatus 300 and variousdata.

(3) Processing Unit 330

The processing unit 330 provides various functions of the terminalapparatus 300. The processing unit 330 includes a reception processingunit 331 and a transmission processing unit 333. Note that theprocessing unit 330 can further include other constituent elementsbesides these constituent elements. That is, the processing unit 330 canperform operations other than the operations of these constituentelements. Specific operations of the reception processing unit 331 andthe transmission processing unit 333 will be described in detail later.

For example, the processing unit 330 communicates with base stations(for example, the base station 100 and/or the base station 200) via theradio communication unit 310.

(4) Implementation Example

The radio communication unit 310 may be implemented by an antenna, aradio frequency (RF) circuit, or the like. The storage unit 320 may beimplemented by a memory (for example, a nonvolatile memory and/or avolatile memory) and/or a hard disk or the like. The processing unit 330may be implemented by a baseband (BB) processor and/or anotherprocessor. The reception processing unit 331 and the transmissionprocessing unit 333 may be implemented by the same processor, or may beimplemented separately by different processors. The aforesaid memory(storage unit 320) may be included in such a processor (chip).

The terminal apparatus 300 may include a memory which stores a programand one or more processors capable of executing the program. The one ormore processors may perform the operation of the processing unit 330(reception processing unit 331 and transmission processing unit 333).The program may be a program for causing the one or more processors toexecute the operation of the processing unit 330 (reception processingunit 331 and transmission processing unit 333).

<2.5. Technical Features>

Next, technical features of the first example embodiment will bedescribed with reference to FIG. 5 to FIG. 8.

In the first example embodiment, the base station 100 (firstcommunication processing unit 141) transmits reference signals usingbeamforming. The terminal apparatus 300 (reception processing unit 331)receives the reference signals. For example, the base station 100 is abase station located around the terminal apparatus 300, and a servingbase station for the terminal apparatus 300 is the base station 200.

Further, the terminal apparatus 300 (transmission processing unit 333)transmits, to the base station 200, first beam related informationrelated to a beam, the first beam related information being informationfor the base station 100, and the base station 200 (first communicationprocessing unit 241) receives the first beam related information fromthe terminal apparatus 300.

Further, a handover of the terminal apparatus 300 from the base station200 (source base station) to the base station 10 (target) is performed.The base station 200 (second communication processing unit 243)transmits, to the base station 100, a handover message (for example, aHANDOVER REQUEST message) including second beam related informationcorresponding to the first beam related information, and the basestation 100 (second communication processing unit 143) receives thehandover message from the base station 200.

In particular, in the first example embodiment, the base station 100(first communication processing unit 141) receives an access signal ofthe terminal apparatus 300 based on the second beam related information.

(1) Transmission of Reference Signals

Plurality of Beams

For example, the base station 100 (first communication processing unit141) transmits the reference signals by a plurality of beams. Theplurality of beams can be said as beams by which the base station 100transmits signals (or beams formed by the base station 100 to transmitsignals). The beams are beams directed in different directions. The beamhere means a directional beam, and for example, is formed by multiplyinga signal by a set of beamforming weights and transmitting the signalresulting from the multiplication, using the directional antenna.Hereinafter, specific examples of the plurality of beams will bedescribed with reference to FIG. 5.

FIG. 5 is an explanatory diagram for explaining an example of theplurality of beams by which the reference signals are transmitted.Referring to FIG. 5, the base station 100, the cell 10, and sixteenbeams 11 (beams 11A to 11P) are illustrated. For example, the basestation 100 transmits the reference signals by the sixteen beams 11 inthis manner. As one example, the beams are each identified by abeamindex (or a weight index). For example, the beam 11A is identified by anindex #0, and the beam 11J is identified by an index #9.

Radio Resource

For example, the base station 100 (first communication processing unit141) transmits the reference signals by the plurality of beams, usingradio resources which are different for the respective beams.

As a first example, the radio resource is a time resource. That is, thebase station 100 transmits the reference signals by the plurality ofbeams, using the time resources which are different for the respectivebeams.

FIG. 6 is an explanatory diagram for explaining an example of the radioresources (time resources) used for the transmission of the referencesignals. Referring to FIG. 6, sixteen time slots (time slots #0 to #15)which are in a row in a time direction are illustrated. In this example,in a beam search period 30 including the sixteen time slots, thereference signals are transmitted by the sixteen beams. For example, inthe time slot #0, the reference signals are transmitted by the beam #0(beam 11A), and in the time slot #1, the reference signals aretransmitted by the beam #1 (beam 11B). Similarly, in the time slot #9,the reference signals are transmitted by the beam #9 (beam 11J). In thisexample, the time slots in which the reference signals are transmittedby the beams are continuous, but the time slots need not be continuousand may be discrete. Note that the time slot here may be called asubframe, or may be called simply a slot.

As a second example, the radio resource may be a frequency resource.That is, the base station 100 may transmit the reference signals by theplurality of beams, using the frequency resources which are differentfor the respective beams. For example, the base station 100 may transmitthe reference signals by the beam #0 (beam 11A) in a first band (forexample, a band having a width of one resource block or more) in afrequency band, and transmit the reference signals by the beam #1 (beam11B) in a second band of this frequency band. Alternatively, the basestation 100 may transmit the reference signals by the beam #0 (beam 11A)using a first carrier (for example, one subcarrier or more) in a blockband (for example, a band with a resource block width) included in thefrequency band, and transmit the reference signals by the beam #1 (beam11B) using a second carrier in this block band.

As a third example, the radio resource may be a time-frequency resource.That is, the base station 100 may transmit the reference signals by theplurality of beams using the time-frequency resources which aredifferent for the respective beams. For example, the base station 100may transmit the reference signals by the beam #0 (beam IA) using afirst time-frequency resource (for example, one resource element ormore), and transmit the reference signals by the beam #1 (beam 11B)using a second time-frequency resource.

Consequently, even when the base station 100 transmits reference signalscommon to the beams, it is possible for the terminal apparatus toidentify a beam used for the transmission of the reference signals.

A relation between the beams and the radio resources may be staticallydetermined (for example, in a standard), or may be configured by anoperator or a network.

Note that the base station 100 (first communication processing unit 141)may transmit reference signals which are different for the respectivebeams, instead of using the radio resources which are different for therespective beams. This enables the terminal apparatus to identify a beamused for the transmission of a reference signal.

(2) Measurement Report

For example, the terminal apparatus 300 (reception processing unit 331)performs the measurements of the reference signals transmitted by thebase station 100 using the beamforming.

For example, the terminal apparatus 300 (transmission processing unit333) transmits a measurement report to the base station 200. Themeasurement report includes measurement results of the reference signalswhich are transmitted by the base station 100 using the beamforming. Inparticular, the measurement report further includes the aforesaid firstbeam related information.

More specifically, for example, the terminal apparatus 300 performs themeasurements of the reference signals transmitted by each of the beams,to select a beam accompanied by the best measurement results (forexample, the highest received power or received quality). In otherwords, the terminal apparatus 300 selects a preferred beamformingweight. Then, the terminal apparatus 300 transmits, to the base station200, the measurement report including the first beam related informationassociated with the selected beam and the best measurement results.

FIG. 7 is an explanatory diagram for explaining an example of themeasurement report of the terminal apparatus 300. Referring to FIG. 7,the base station 100 and the terminal apparatus 300 are illustrated. Forexample, the terminal apparatus 300 performs the measurements of thereference signals transmitted by the beams, to select the beam #9 (beam11J) accompanied by the best measurement results. Then, the terminalapparatus 300 transmits, to the base station 200, the measurement reportincluding the first beam related information related to the beam #9(beam 11J) (for example, the beam index/weight index #9) and the bestmeasurement results.

Consequently, for example, it is possible for the base station 200 toobtain the first beam related information for the base station 100through the measurement report.

(3) Handover Message

As described above, the base station 200 (source base station)transmits, to the base station 100 (target base station), the handovermessage including the second beam related information. The handovermessage may be transmitted from the base station 200 directly to thebase station 100 (for example, in a case of an X2 handover), or may betransmitted from the base station 200 to the base station 100 via a corenetwork (for example, in a case of an S handover).

For example, the handover message is a HANDOVER REQUEST message.Hereinafter, an example of the first example embodiment will bedescribed, assuming that the handover message is the HANDOVER REQUESTmessage. However, the handover message used in the first exampleembodiment is not limited to the HANDOVER REQUEST message, but may beanother message transmitted from the source base station to the targetbase station in the handover procedure.

(4) Beam Related Information

Relation of the First Beam Related Information and the Second BeamRelated Information

As described above, the second beam related information corresponds tothe first beam related information.

For example, the second beam related information is the same informationas the first beam related information. That is, the base station 200includes, in the HANDOVER REQUEST message, the second beam relatedinformation which is the same as the first beam related informationreceived from the terminal apparatus 300 and transmits the HANDOVERREQUEST message to the base station 100.

Alternatively, the second beam related information may be informationdifferent from the first beam related information. For example, the basestation 20 may convert the first beam related information to the secondbeam related information to transmit, to the base station 100, theHANDOVER REQUEST message including this second beam related information.

Examples of the Beam Related Information

The beam related information (the first beam related information and thesecond beam related information) is information related to a beam. Sincethe beam is formed using the beamforming weights (set(s) of thebeamforming weights), the beams can have a one-to-one correspondencewith the set(s) of the beamforming weights. Therefore, the beam relatedinformation can also be said as information related to the beamformingweight (for example, weight related information).

The beam related information is information for the base station 100.For example, the beam related information is information related to abeam of the base station 100 (beam to be used by the base station 100 totransmit a signal).

For example, the beam related information is information related to oneof the plurality of beams. Specifically, for example, the beam relatedinformation is information indicating one of the plurality of beams, inother words, is information enabling the identification of one of theplurality of beams (for example, beam identification information). Asone example, the beam related information is a beam index.Alternatively, the beam related information may be informationindicating one of the plurality of set(s) of the beamforming weights, inother words, may be information enabling the identification of one ofthe plurality of sets (for example, weight identification information).As one example, the beam related information may be a weight index.Since the beam is formed using the set(s) of the beamforming weights,the beams can have a one-to-one correspondence with the set(s) of thebeamforming weights. Therefore, the beam related information may beinformation indicating one of the plurality of beams (beam index), andmay be the aforesaid information indicating one of the plurality of sets(weight index). That is, the beam index and the weight index, thoughnamed differently, may be the same index. As a matter of course, thebeam related information may be information with another name (beam ID,weight ID, beamforming index, beamforming ID, or the like) enabling theidentification of the beam or the set of the beamforming weights.

(5) Reception of Access Signal

In particular, in the first example embodiment, the base station 100(first communication processing unit 141) receives the access signal ofthe terminal apparatus 300 based on the second beam related information.

For example, the base station 100 (first communication processing unit141) receives the access signal, using the set of the beamformingweights corresponding to the second beam related information.Specifically, for example, the second beam related information is thebeam index or the weight index, and the base station 100 identifies theset of the beamforming weights from the beam index or the weight index.Then, the base station 100 receives the access signal, using this set ofthe beamforming weights. That is, the base station 100 performs uplinkbeamforming processing by multiplying the access signal by the aforesaidset of the beamforming weights.

The access signal may be an uplink signal to be used in initial accessfor transiting from an idle state (for example, RRC_Idle) to an activestate or a connected state (for example, RRC_Connected), or to be usedin access to a target cell at the time of the execution of the handover.Alternatively, the access signal may be an uplink signal in there-establishment of radio connection (RRC Connection Re-establishment)for the recovery of the radio connection. The uplink signal may be arandom access signal (for example, a random access preamble signal), acontrol signal transmitted on an uplink data channel (for example, PUSCH(Physical Uplink Shared Channel)), or a control signal transmitted on anuplink control channel (for example, PUCCH (Physical Uplink ControlChannel)). In the system 1 of the first example embodiment, unlike theart disclosed in patent literature (JP2014-531852T), the terminalapparatus 300 does not communicate with the base station 100 in advance(by ranging and a response thereto), but starts the communication withthe base station 100 using the access signal. Therefore, a success inreceiving the access signal is very important.

Thus receiving the access signal using the second beam relatedinformation ensures, for example, the compensation of a propagation lossof the signal, resulting in an increased possibility of the success ofreceiving the access signal. This can further increase the possibilityof the success of the handover.

Note that, for example, a set of beamforming weights for uplink is thesame as a set of beamforming weights for downlink. Alternatively, theset of the beamforming weights for uplink may be different from the setof the beamforming weights for downlink.

(6) Flow of Processing

An example of processing according to the first example embodiment willbe described with reference to FIG. 8. FIG. 8 is a sequence diagram forexplaining an example of a schematic flow of the processing according tothe first example embodiment.

The terminal apparatus 300 performs the measurements of referencesignals transmitted by the base station 100 using beamforming, to selecta preferred beamforming weight. Then, the terminal apparatus 300transmits, to the base station 200 (serving base station), a measurementreport including a weight index indicating the preferred beamformingweight (S401). The measurement report includes measurement results ofthe reference signals.

Thereafter, a handover of the terminal apparatus 300 from the basestation 200 (source base station) to the base station 100 (target basestation) is decided, and the base station 200 transmits, to the basestation 100, a HANDOVER REQUEST message including the weight indexindicating the preferred beamforming weight (S403).

The base station 100 obtains the weight index included in the HANDOVERREQUEST message and transmits, to the base station 200, a HANDOVERREQUEST ACKNOWLEDGE message including a HandoverCommand message of anRRC layer corresponding to an instruction of the handover (S405).

The base station 200 transmits, to the terminal apparatus 300, an RRCsignal (for example, an RRCConnectionReconfiguration message) includingthe HandoverCommand message (S407).

The terminal apparatus 300 transmits an access signal to the basestation 100 (S409). The base station 100 receives the access signalbased on the weight index. That is, the base station 100 receives theaccess signal, using the beamforming weight indicated by the weightindex.

Note that the example of the flow of the processing described above isonly schematic, and as a matter of course, transmission/reception otherthan those at Steps S401 to S409 described above can be performed in thefirst example embodiment.

(7) Meaning of “Transmit”

“Transmit” here means, for example, that transmission processing in atleast one protocol layer out of a plurality of protocol layers isperformed, and does not mean that a signal is output by wire or byradio. Similarly, “receive” here means, for example, that receptionprocessing in at least one protocol layer out of a plurality of protocollayers is performed. As one example, the plurality of protocol layersincludes a physical layer, a MAC (Media Access Control) layer, a RLC(Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol)layer, and a RRCS (Radio Resource Control) layer. As another example,the plurality of protocol layers includes a physical layer, a MAC layer,an IP (Internet Protocol) layer, and a transport layer.

Further, “transmit X to Y” here is not limited to the transmission of Xdirectly to Y but includes the transmission of X indirectly to Y (thatis, X is transmitted to another node and X is transmitted to Y through atransfer by the other node). Similarly, “receive X from Y” here is notlimited to the reception of X directly from Y, but includes thereception of X indirectly from Y (that is, X transmitted by Y isreceived through the transfer by another node).

<2.6. Example Alterations>

Next, example alterations of the first example embodiment will bedescribed with reference to FIG. 9 to FIG. 11.

(1) First Example Alteration

Resource Information

In a first example alteration of the first example embodiment, forexample, the base station 100 (second communication processing unit 143)transmits, to the base station 200, resource information indicating aradio resource for transmitting the access signal, and the base station200 (second communication processing unit 243) receives the resourceinformation.

Then, the base station 200 (first communication processing unit 241)transmits the resource information to the terminal apparatus 300 and theterminal apparatus 300 (reception processing unit 331) receives theresource information.

Thereafter, the terminal apparatus 3 (transmission processing unit 333)transmits the access signal to the base station 100 based on theresource information. That is, the terminal apparatus 300 (transmissionprocessing unit 333) transmits the access signal to the base station100, using the radio resource indicated by the resource information. Thebase station 100 receives (based on the aforesaid second beam relatedinformation) the access signal which is transmitted using the radioresource.

Consequently, for example, it is possible for the base station 100 tomore easily receive the access signal of the terminal apparatus 300.

The resource information may be called a Dedicated RACH (Random AccessChannel) Resource Information.

Radio Resource

For example, the aforesaid radio resource is a radio resource for a beamor a set of beamforming weights corresponding to the second beam relatedinformation.

More specifically, for example, access radio resources are prepared forthe respective beams or the respective set(s) of the beamformingweights. For example, the second beam related information indicates abeam or a set of beamforming weights, and the radio resource indicatedby the resource information is a radio resource for this beam or thisset of the beamforming weights.

FIG. 9 is an explanatory diagram for explaining an example of the radioresources indicated by the resource information. Referring to FIG. 9, Ntime slots included in each radio frame are illustrated. In thisexample, access radio resources are prepared in the respective timeslots. For example, the time slot #0 is an access radio resource of thebeam #0. In this case, in the time slot #0, the base station 100receives the access signal using a set of beamforming weights identifiedby the beam index (or the weight index) #0. For example, the time slot#N−1 is an access radio resource of the beam #15. In this case, in thetime slot #N−1, the base station 100 receives the access signal using aset of beamforming weights identified by the beam index (or weightindex) #15.

Consequently, for example, it is possible for the base station 100 tofurther easily receive the access signal of the terminal apparatus 300.This is because, when receiving the access signal, the base station 100need not use various sets of beamforming weights but only need to use aspecific set of beamforming weights.

Retransmission Cycle Information

For example, the base station 100 (second communication processing unit143) transmits, to the base station 200, retransmission cycleinformation indicating a retransmission cycle of the access signal, withthe resource information, and the base station 200 (second communicationprocessing unit 243) receives the retransmission cycle information.

Then, the base station 200 (first communication processing unit 241)transmits the retransmission cycle information to the terminal apparatus300, and the terminal apparatus 300 (reception processing unit 331)receives the retransmission cycle information.

Thereafter, the terminal apparatus 300 (transmission processing unit333) retransmits the access signal to the base station 100 based on theretransmission cycle information. That is, the terminal apparatus 300(transmission processing unit 333) retransmits the access signal to thebase station 100 with a retransmission cycle indicated by theretransmission cycle information.

Consequently, for example, it is possible for the base station 100 tomore easily receive the retransmitted access signal as well.

The retransmission cycle information may be called RACH (Random AccessChannel) Retransmission cycle Information.

Message

For example, the base station 1 (second communication processing unit143) transmits, to the base station 200, a response message to theaforesaid HANDOVER REQUEST message, and the base station 200 (secondcommunication processing unit 243) receives the response message. Theresponse message may be transmitted from the base station 100 directlyto the base station 200 (for example, in a case of an X2 handover), ormay be transmitted from the base station 100 to the base station 200 viaa core network (for example, in a case of an Si handover). Inparticular, the response message includes the resource information andthe retransmission cycle information. Specifically, for example, theresponse message is a HANDOVER REQUEST ACKNOWLEDGE message. Further, forexample, the HANDOVER REQUEST ACKNOWLEDGE message includes an RRCContainer, and the RRC Container includes a HandoverCommand message.Further, for example, the HandoverCommand message includes anRRCConnectionReconfiguration message, and theRRCConnectionReconfiguration message includes the resource informationand the retransmission cycle information. As a matter of course, thefirst example embodiment is not limited to this example, and theresponse message may include the resource information and theretransmission cycle information in a different manner.

For example, the base station 200 (first communication processing unit241) transmits (transfers), to the terminal apparatus 300, theHandoverCommand message (included in the response message), and theterminal apparatus 300 (reception processing unit 331) receives theHandoverCommand message. As described above, the HandoverCommand messageincludes the resource information and the retransmission cycleinformation.

Flow of Processing

FIG. 10 is a sequence diagram for explaining an example of a schematicflow of processing of the first example alteration of the first exampleembodiment. Descriptions of Steps S421, S423 illustrated in FIG. 10 arethe same as the descriptions of, for example, Steps S401, S403illustrated in FIG. 8. Therefore, overlapping descriptions will beomitted here, and only Steps S425, S427, S429 will be described.

The base station 100 obtains a weight index included in a HANDOVERREQUEST message. Then, the base station 100 generates Dedicated RACHResource Information indicating a radio resource for a set ofbeamforming weights indicated by the weight index. Thereafter, the basestation 100 transmits, to the base station 200, a HandoverCommandmessage including the Dedicated RACH Resource Information, in a HANDOVERREQUEST ACKNOWLEDGE message (S425). The HandoverCommand message mayfurther include RACH Retransmission cycle Information.

The base station 200 transfers the HandoverCommand message to theterminal apparatus 300 (S427).

The terminal apparatus 300 transmits an access signal to the basestation 100, using a radio resource indicated by the Dedicated RACHResource Information (S429). Based on the weight index, the base station100 receives the access signal transmitted using the radio resource.That is, the base station 100 receives the access signal transmittedusing the radio resource (radio resource for the set of the beamformingweights), using the set of the beamforming weights indicated by theweight index. Incidentally, if retransmission is necessary, the terminalapparatus 300 retransmits the access signal to the base station 100,with a retransmission cycle indicated by the Dedicated RACHRetransmission cycle Information.

Note that the example of the flow of the processing described above isonly schematic, and as a matter of course, in the first examplealteration of the first example embodiment, transmission/reception otherthan those at Steps S421 to S429 described above can be performed.

Alternate Method

In the above-described example, the base station 100 transmits, to thebase station 200, the resource information indicating the radio resourcefor transmitting the access signal, and the base station 200 receivesthe resource information, but the first example alteration is notlimited to this example.

Instead of that the base station 100 transmits the resource informationto the base station 200, the base station 200 (first communicationprocessing unit 241) may generate the resource information. In thiscase, the base station 200 may receive, from the base station 100information necessary for generating the resource information (forexample, information indicating a radio resource for each beam), inadvance.

Consequently, for example, it is possible to reduce a volume ofinformation transmitted/received between the base station 100 and thebase station 200.

(2) Second Example Alteration

In a second example alteration of the first example embodiment, forexample, the base station 100 (second communication processing unit 143)transmits, to the base station 200, beamforming configurationinformation related to a configuration of beamforming of the basestation 100. Then, the base station 200 (second communication processingunit 243) receives the beamforming configuration information.

Further, the base station 200 (first communication processing unit 241)transmits the beamforming configuration information to the terminalapparatus 300, and the terminal apparatus (reception processing unit331) receives the beamforming configuration information.

Then, based on the beamforming configuration information, the terminalapparatus 300 (reception processing unit 331) receives reference signalstransmitted by the base station 100 using the beamforming. For example,the terminal apparatus 300 (reception processing unit 331) performs themeasurements of the reference signals based on the beamformingconfiguration information.

Consequently, for example, it is possible to use a configuration ofbeamforming suitable for the base station or the cell, and it ispossible for the terminal apparatus 3 to perform thereception/measurements according to the configuration.

Configuration Information

For example, the beamforming configuration information includes beamnumber information indicating the number of beams. In the example inFIG. 5, the beam number information indicates 16 as the number of thebeams. Consequently, it is possible to use beams in number according toproperties (for example, size) of the cell.

For example, the beamforming configuration information includes beamresource information indicating radio resources for respective beams fortransmitting the reference signals. For example, as described withreference to FIG. 6, the radio resource is the time resource for eachbeam. In this case, for example, the beam resource information includesa period and an offset in a time direction. Alternatively, the radioresource may be the frequency resource for each beam. In this case, thebeam resource information may include a period and an offset in afrequency direction. Alternatively, the radio resource may be thetime-frequency resource for each beam. In this case, the beam resourceinformation may be information indicating a pattern of the radioresource. This makes it possible to, for example, more flexibly set aradio resource to be used for the transmission of the reference signalsusing the beamforming.

Message

For example, the base station 100 (second communication processing unit143) transmits, to the base station 200, the beam forming configurationinformation at the time of the setup of an interface between the basestation 10 and the base station 200. Then, the base station 200 (secondcommunication processing unit 243) receives the beamformingconfiguration information.

Specifically, for example, the base station 100 (second communicationprocessing unit 143) transmits, to the base station 200, an X2 SETUPREQUEST message or an X2 SETUP RESPONSE message. Then, the base station200 (second communication processing unit 243) receives the X2 SETUPREQUEST message or the X2 SETUP RESPONSE message. In particular, the X2SETUP REQUEST message or the X2 SETUP RESPONSE message includes thebeamforming configuration information.

For example, the base station 200 (first communication processing unit241) transmits a measurement configuration to the terminal apparatus300, and the terminal apparatus 300 (reception processing unit 331)receives the measurement configuration. In particular, the measurementconfiguration includes the beamforming configuration information.

Flow of Processing

FIG. 11 is a sequence diagram for explaining an example of a schematicflow of processing of the second example alteration of the first exampleembodiment. Descriptions of Steps S449 to S455 illustrated in FIG. 11 isthe same as, for example, the descriptions of Steps S403 to S409illustrated in FIG. 8. Therefore, overlapping descriptions will beomitted here, and only Steps S441 to S447 will be described.

The base station 200 transmits an X2 SETUP REQUEST message to the basestation 100 (S441), and in response to this, the base station 100transmits an X2 SETUP RESPONSE message to the base station 200 (S443).The X2 SETUP RESPONSE message includes beamforming configurationinformation related to a configuration of beamforming of the basestation 100.

Further, the base station 200 transmits a measurement configurationincluding the beamforming configuration information to the terminalapparatus 300 (S445).

Based on the beamforming configuration information, the terminalapparatus 300 performs the measurements of reference signals transmittedby the base station 100 using the beamforming, and selects a preferredbeamforming weight. Then, the terminal apparatus 300 transmits, to thebase station 200 (serving base station), a measurement report includinga weight index indicating the preferred beamforming weight (S447). Themeasurement report includes measurement results of the referencesignals.

(3) Third Example Alteration

When the terminal apparatus 300 attempts the reconnection to the sametarget cell at the time when a handover of the terminal apparatus 300fails, the base station 100 (first communication processing unit 141)may also receive an access signal of the terminal apparatus 300 based onthe second beam related information, as in the above-described exampleof the first example embodiment.

Further, when the terminal apparatus 300 attempts the reconnection tothe same target cell at the time when a handover of the terminalapparatus 300 fails, the terminal apparatus 300 (transmission processingunit 333) may also transmit an access signal to the base station 100based on the resource information, as in the first example alteration ofthe first example embodiment.

Hereinabove, the example alterations of the first example embodimenthave been described. Note that two or more of the first to third examplealterations may be combined. That is, a combination of the technicalfeatures of two or more of the first to third example alterations may beintroduced.

3. Second Example Embodiment

Next, a second example embodiment of the present invention will bedescribed with reference to FIG. 12 to FIG. 16. The above-describedfirst example embodiment is a specific example embodiment, but thesecond example embodiment is a more generalized example embodiment.

<3.1. Configuration of System>

An example of the configuration of a system 2 according to the secondexample embodiment will be described with reference to FIG. 12. FIG. 12is an explanatory diagram illustrating an example of the schematicconfiguration of the system 2 according to the second exampleembodiment. Referring to FIG. 12, the system 2 includes a base station500, a base station 600, and a terminal apparatus 700.

For example, the system 2 may be a system conforming to the standard of3GPP. More specifically, the system 2 may be, for example, a systemconforming to the standard of the Fifth Generation (5G).

For example, descriptions of the base station 500, the base station 600,and the terminal apparatus 700 are the same as the descriptions of thebase station 100, the base station 200, and the terminal apparatus 300of the first example embodiment. Therefore, overlapping descriptionswill be omitted here.

<3.2 Configuration of Base Station 500>

Next, an example of the configuration of the base station 500 of thesecond example embodiment will be described with reference to FIG. 13.FIG. 13 is a block diagram illustrating an example of the schematicconfiguration of the base station 50) of the second example embodiment.Referring to FIG. 13, the base station 500 includes a firstcommunication processing unit 510 and a second communication processingunit 520.

Specific operations of the first communication processing unit 510 andthe second communication processing unit 520 will be described later.

The first communication processing unit 510 and the second communicationprocessing unit 520 may be implemented by a baseband (BB) processorand/or another processor, or the like. The first communicationprocessing unit 510 and the second communication processing unit 520 maybe implemented by the same processor or may be implemented separately bydifferent processors.

The base station 500 may include a memory storing a program and one ormore processors capable of executing the program. The one or moreprocessors may perform the operations of the first communicationprocessing unit 510 and the second communication processing unit 520.The program may be a program for causing the one or more processors toexecute the operations of the first communication processing unit 510and the second communication processing unit 520.

<3.3. Configuration of Base Station 600>

Next, an example of the configuration of the base station 600 of thesecond example embodiment will be described with reference to FIG. 14.FIG. 14 is a block diagram illustrating an example of the schematicconfiguration of the base station 600 of the second example embodiment.Referring to FIG. 14, the base station 600 includes a firstcommunication processing unit 610 and a second communication processingunit 620.

Specific operations of the first communication processing unit 610 andthe second communication processing unit 620 will be described later.

The first communication processing unit 610 and the second communicationprocessing unit 620 may be implemented by a baseband (BB) processorand/or another processor, or the like. The first communicationprocessing unit 610 and the second communication processing unit 620 maybe implemented by the same processor or may be implemented separately bydifferent processors.

The base station 600 may include a memory storing a program and one ormore processors capable of executing the program. The one or moreprocessors may perform the operations of the first communicationprocessing unit 610 and the second communication processing unit 620.The program may be a program for causing the one or more processors toexecute the operations of the first communication processing unit 610and the second communication processing unit 620.

<3.4. Configuration of Terminal Apparatus 700>

Next, an example of the configuration of the terminal apparatus 700 ofthe second example embodiment will be described with reference to FIG.15. FIG. 15 is a block diagram illustrating an example of the schematicconfiguration of the terminal apparatus 700 of the second exampleembodiment. Referring to FIG. 15, the terminal apparatus 700 includes areception processing unit 710 and a transmission processing unit 720.

Specific operations of the reception processing unit 710 and thetransmission processing unit 720 will be described later.

The reception processing unit 710 and the transmission processing unit720 may be implemented by a baseband (BB) processor and/or anotherprocessor, or the like. The reception processing unit 710 and thetransmission processing unit 720 may be implemented by the sameprocessor or may be implemented separately by different processors.

The terminal apparatus 700 may include a memory storing a program andone or more processors capable of executing the program. The one or moreprocessors may perform the operations of the reception processing unit710 and the transmission processing unit 720. The program may be aprogram for causing the one or more processors to execute the operationsof the reception processing unit 710 and the transmission processingunit 720.

<3.5. Technical Features>

Next, technical features of the second example embodiment will bedescribed with reference to FIG. 16.

In the second example embodiment, the base station 500 (firstcommunication processing unit 510) transmits reference signals usingbeamforming. The terminal apparatus 700 (reception processing unit 710)receives the reference signals.

Further, the terminal apparatus 700 (transmission processing unit 720)transmits, to the base station 600, first beam related informationrelated to a beam, the first beam related information being informationfor the base station 500, and the base station 600 (first communicationprocessing unit 610) receives the first beam related information.

Further, a handover of the terminal apparatus 700 from the base station600 (source base station) to the base station 500 (target) is performed.The base station 600 (second communication processing unit 620)transmits, to the base station 500, a handover message (for example, aHANDOVER REQUEST message) including second beam related informationcorresponding to the first beam related information, and the basestation 500 (second communication processing unit 520) receives thehandover message.

In particular, in the second example embodiment, the base station 500(first communication processing unit 510) receives an access signal ofthe terminal apparatus 700 based on the second beam related information.

(1) Transmission of reference signals, measurement report, handovermessage, beam related information, reception of access signal, andmeaning of “transmit”

For example, descriptions of the transmission of the reference signals,a measurement report, the handover message, the beam relatedinformation, the reception of the access signal, and the meaning of“transmit” in the second example embodiment are the same as thedescriptions of these in the first example embodiment. Therefore,overlapping descriptions will be omitted here, and only an example of aschematic flow of processing will be described.

(2) Flow of processing

FIG. 16 is a sequence diagram for explaining an example of the schematicflow of the processing according to the second example embodiment.

The terminal apparatus 700 transmits, to the base station 600, firstbeam related information related to a beam, the first beam relatedinformation being information for the base station 500, and the basestation 600 receives the first beam related information (S801).

The base station 600 transmits, to the base station 500, a handovermessage (for example, a HANDOVER REQUEST message) including second beamrelated information corresponding to the first beam related information,and the base station 500 receives the handover message (S803).

The base station 500 receives an access signal of the terminal apparatus7X) based on the second beam related information (S805).

While the example embodiments of the present invention have beendescribed above, the present invention is not limited to the abovedescribed example embodiments. It will be understood by those skilled inthe art that the above described example embodiments are merely examplesand various alterations and modifications can be made without departingfrom the scope and the spirit of the present invention.

For example, the steps in the processing described in the specificationdo not necessarily have to be executed in a time-series manner along theorder described as the sequence diagrams. For example, the steps in theprocessing may be executed in a different order from the order describedas the sequence diagrams or may be executed in parallel. Further, partof the steps in the processing may be deleted, and more steps may beadded to the processing.

Further, apparatuses or modules thereof (for example, basebandprocessors or other chips) including the constituent elements (forexample, the first communication processing units and/or the secondcommunication processing units) of the base stations described in thespecification may be provided. Similarly, modules (for example, basebandprocessors or other chips) including the constituent elements (forexample, the reception processing unit and/or the transmissionprocessing unit) of the terminal apparatus described in thespecification may be provided. Further, methods each including theprocessing of the constituent elements may be provided, and programseach for causing a processor to execute the processing of theconstituent elements may be provided. Further, recording mediums(computer-readable non-transitory recording mediums) each recording theprogram may be provided. As a matter of course, such apparatuses,modules, methods, programs and recording mediums are also included inthe present invention.

Some or all of the above-described example embodiments can be describedas the following supplementary notes, but are not limited to thefollowing supplementary notes.

(Supplementary Note 1)

An apparatus including:

a first communication processing unit configured to transmit referencesignals using beamforming; and

a second communication processing unit configured to receive a handovermessage from a source base station of a handover of a terminalapparatus,

wherein the handover message includes beam related information relatedto a beam, and

wherein the first communication processing unit is configured to receivean access signal of the terminal apparatus based on the beam relatedinformation.

(Supplementary Note 2)

The apparatus according to supplementary note 1, wherein the firstcommunication processing unit is configured to receive the accesssignal, using a set of beamforming weights that corresponds to the beamrelated information.

(Supplementary Note 3)

The apparatus according to supplementary note 1 or 2, wherein the accesssignal is an uplink signal in random access of the terminal apparatus.

(Supplementary Note 4)

The apparatus according to any one of supplementary notes 1 to 3,wherein the second communication processing unit is configured totransmit, to the source base station, resource information indicating aradio resource for transmitting the access signal.

(Supplementary Note 5)

The apparatus according to supplementary note 4, wherein the radioresource is a radio resource for a beam or a set of the beamformingweights that corresponds to the beam related information.

(Supplementary Note 6)

The apparatus according to supplementary note 4 or 5, wherein the secondcommunication processing unit is configured to transmit, to the sourcebase station, a response message to the handover message, and whereinthe response message includes the resource information.

(Supplementary Note 7)

The apparatus according to any one of supplementary notes 4 to 6,wherein the second communication processing unit is configured totransmit, to the source base station, retransmission cycle informationindicating a retransmission cycle of the access signal, with theresource information.

(Supplementary Note 8)

The apparatus according to any one of supplementary notes 4 to 7,wherein the resource information is information to be transmitted fromthe source base station to the terminal apparatus.

(Supplementary Note 9)

The apparatus according to any one of supplementary notes 1 to 8,wherein the first communication processing unit is configured totransmit reference signals by a plurality of beams.

(Supplementary Note 10)

The apparatus according to supplementary note 9, wherein the firstcommunication processing unit is configured to transmit referencesignals by the plurality of beams, using radio resources that aredifferent for the respective beams.

(Supplementary Note 11)

The apparatus according to supplementary note 10, wherein the radioresources are frequency resources, time resources, or time-frequencyresources.

(Supplementary Note 12)

The apparatus according to any one of supplementary notes 1 to 11,wherein the beam related information is information related to one of aplurality of beams.

(Supplementary Note 13)

The apparatus according to supplementary note 12, wherein the beamrelated information is information indicating one of the plurality ofbeams.

(Supplementary Note 14)

The apparatus according to supplementary note 12 or 13, wherein the beamrelated information is information indicating one of a plurality of setsof beamforming weights.

(Supplementary Note 15)

The apparatus according to any one of supplementary notes 1 to 14,wherein the beam related information corresponds to beam relatedinformation transmitted from the terminal apparatus to the source basestation.

(Supplementary Note 16)

The apparatus according to any one of supplementary notes 1 to 15,wherein the second communication processing unit is configured totransmit, to the source base station, beamforming configurationinformation related to a configuration of beamforming.

(Supplementary Note 17)

The apparatus according to supplementary note 16, wherein thebeamforming configuration information includes information indicatingthe number of beams and information indicating radio resources forrespective beams for transmitting reference signals.

(Supplementary Note 18)

The apparatus according to supplementary note 16 or 17, wherein thebeamforming configuration information is information to be transmittedfrom the source base station to the terminal apparatus.

(Supplementary Note 19)

The apparatus according to any one of supplementary notes 1 to 18, theapparatus being a base station, one or more apparatuses of a pluralityof apparatuses included in a base station, or a module for one of theplurality of apparatuses.

(Supplementary Note 20)

An apparatus including:

a first communication processing unit configured to receive, from aterminal apparatus, first beam related information related to a beam,the first beam related information being information for a base stationwhich transmits reference signals using beamforming; and

a second communication processing unit configured to transmit, to thebase station, a handover message including second beam relatedinformation corresponding to the first beam related information,

wherein the second beam related information is information to be used bythe base station to receive an access signal of the terminal apparatus.

(Supplementary Note 21)

The apparatus according to supplementary note 20, wherein the firstcommunication processing unit is configured to transmit, to the terminalapparatus, resource information indicating a radio resource fortransmitting the access signal.

(Supplementary Note 22)

The apparatus according to supplementary note 21, wherein the firstcommunication processing unit is configured to transmit, to the terminalapparatus, retransmission cycle information indicating a retransmissioncycle of the access signal, with the resource information.

(Supplementary Note 23)

The apparatus according to supplementary note 21 or 22,

wherein the first communication processing unit is configured totransmit a HandoverCommand message to the terminal apparatus, and

wherein the HandoverCommand message includes the resource information.

(Supplementary Note 24)

The apparatus according to any one of supplementary notes 21 to 23,wherein the second communication processing unit is configured toreceive the resource information from the base station.

(Supplementary Note 25)

The apparatus according to any one of supplementary notes 21 to 23,wherein the first communication processing unit is configured togenerate the resource information.

(Supplementary Note 26)

The apparatus according to any one of supplementary notes 20 to 25,wherein the second beam related information is information that is thesame as the first beam related information.

(Supplementary Note 27)

The apparatus according to any one of supplementary notes 20 to 26,wherein the first beam related information and the second beam relatedinformation is information related to one of a plurality of beams.

(Supplementary Note 28)

The apparatus according to any one of supplementary notes 20 to 27,

wherein the first communication processing unit is configured to receivea measurement report transmitted from the terminal apparatus, and

wherein the measurement report includes the first beam relatedinformation,

(Supplementary Note 29)

The apparatus according to any one of supplementary notes 20 to 28,

wherein the second communication processing unit is configured toreceive, from the base station, beamforming configuration informationrelated to a configuration of beamforming of the base station, and

wherein the first communication processing unit is configured totransmit the beamforming configuration information to the terminalapparatus.

(Supplementary Note 30)

The apparatus according to supplementary note 29,

wherein the first communication processing unit is configured totransmit a measurement configuration to the terminal apparatus, and

wherein the measurement configuration includes the beamformingconfiguration information.

(Supplementary Note 31)

The apparatus according to any one of supplementary notes 20 to 30, theapparatus being a base station, one or more apparatuses of a pluralityof apparatuses included in the base station, or a module for one of theplurality of apparatuses.

(Supplementary Note 32)

An apparatus including:

a reception processing unit configured to receive reference signalstransmitted by a first base station using beamforming; and

a transmission processing unit configured to transmit, to a second basestation, first beam related information related to a beam, the firstbeam related information being information for the first base station,

wherein the first beam related information corresponds to second beamrelated information to be used by the first base station to receive anaccess signal.

(Supplementary Note 33)

The apparatus according to supplementary note 32,

wherein the reception processing unit is configured to receive, from thesecond base station, resource information indicating a radio resourcefor transmitting an access signal, and

wherein the transmission processing unit transmits an access signal tothe first base station based on the resource information.

(Supplementary Note 34)

The apparatus according to supplementary note 33.

wherein the reception processing unit is configured to receive, from thesecond base station, retransmission cycle information indicating aretransmission cycle of the access signal, with the resourceinformation, and

wherein the transmission processing unit is configured to retransmit theaccess signal to the first base station based on the retransmissioncycle information.

(Supplementary Note 35)

The apparatus according to any one of supplementary notes 32 to 34,

wherein the transmission processing unit is configured to transmit ameasurement report to the second base station, and

wherein the measurement report includes the first beam relatedinformation.

(Supplementary Note 36)

The apparatus according to supplementary note 35, wherein themeasurement report includes measurement results of reference signalstransmitted by the first base station using the beamforming.

(Supplementary Note 37)

The apparatus according to any one of supplementary notes 32 to 36,

wherein the reception processing unit is configured to receive, from thesecond base station, beamforming configuration information related to aconfiguration of beamforming of the first base station, and

wherein the reception processing unit is configured to receive referencesignals transmitted by the first base station using beamforming, basedon the beamforming configuration information.

(Supplementary Note 38)

The apparatus according to any one of supplementary notes 32 to 37,wherein the apparatus is a terminal apparatus or a module for a terminalapparatus.

(Supplementary Note 39)

A method including:

transmitting reference signals using beamforming;

receiving a handover message from a source base station of a handover ofa terminal apparatus, the handover message including beam relatedinformation related to a beam; and

receiving an access signal of the terminal apparatus based on the beamrelated information.

(Supplementary Note 40)

A method including:

receiving, from a terminal apparatus, first beam related informationrelated to a beam, the first beam related information being informationfor a base station which transmits reference signals using beamforming;and

transmitting, to the base station, a handover message including secondbeam related information corresponding to the first beam relatedinformation,

wherein the second beam related information is information to be used bythe base station to receive an access signal of the terminal apparatus,

(Supplementary Note 41)

A method including:

receiving reference signals transmitted by a first base station usingbeamforming; and

transmitting, to a second base station, first beam related informationrelated to a beam, the first beam related information being informationfor the first base station,

wherein the first beam related information corresponds to second beamrelated information to be used by the first base station to receive anaccess signal.

(Supplementary Note 42)

A system including:

a first base station;

a second base station; and

a terminal apparatus,

wherein the first base station transmits reference signals usingbeamforming,

wherein the terminal apparatus receives the reference signals, andtransmits, to the second base station, first beam related informationrelated to a beam, the first beam related information being informationfor the first base station,

wherein the second base station transmits, to the first base station, ahandover message including second beam related information correspondingto the first beam related information, and

wherein the first base station receives an access signal of the terminalapparatus based on the second beam related information.

(Supplementary Note 43)

A program for causing a processor to execute:

transmitting reference signals using beamforming;

receiving a handover message from a source base station of a handover ofa terminal apparatus, the handover message including beam relatedinformation related to a beam; and

receiving an access signal of the terminal apparatus based on the beamrelated information.

(Supplementary Note 44)

A program for causing a processor to execute:

receiving, from a terminal apparatus, first beam related informationrelated to a beam, the first beam related information being informationfor a base station which transmits reference signals using beamforming;and

transmitting, to the base station, a handover message including secondbeam related information corresponding to the first beam relatedinformation,

wherein the second beam related information is information to be used bythe base station to receive an access signal of the terminal apparatus.

(Supplementary Note 45)

A program for causing a processor to execute:

receiving reference signals transmitted by a first base station usingbeamforming; and

transmitting, to a second base station, first beam related informationrelated to a beam, the first beam related information being informationfor the first base station,

wherein the first beam related information corresponds to second beamrelated information to be used by the first base station to receive anaccess signal.

(Supplementary Note 46)

A computer-readable non-transitory recording medium having recordedthereon a program for causing a processor to execute:

transmitting reference signals using beamforming;

receiving a handover message from a source base station of a handover ofa terminal apparatus, the handover message including beam relatedinformation related to a beam; and

receiving an access signal of the terminal apparatus based on the beamrelated information.

(Supplementary Note 47)

A computer-readable non-transitory recording medium having recordedthereon a program for causing a processor to execute:

receiving, from a terminal apparatus, first beam related informationrelated to a beam, the first beam related information being informationfor a base station which transmits reference signals using beamforming;and

transmitting, to the base station, a handover message including secondbeam related information corresponding to the first beam relatedinformation,

wherein the second beam related information is information to be used bythe base station to receive an access signal of the terminal apparatus.

(Supplementary Note 48)

A computer-readable non-transitory recording medium having recordedthereon a program for causing a processor to execute:

receiving reference signals transmitted by a first base station usingbeamforming; and

transmitting, to a second base station, first beam related informationrelated to a beam, the first beam related information being informationfor the first base station,

wherein the first beam related information corresponds to second beamrelated information to be used by the first base station to receive anaccess signal.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-152618, filed on Aug. 3, 2016; theentire contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

In a mobile communication system, it is possible to increase apossibility of a success in a handover.

REFERENCE SIGNS LIST

-   -   1, 2 system    -   10, 20 cell/coverage area    -   11 beam    -   30 beam search period    -   100, 200, 500, 600 base station    -   141, 241, 510, 610 first communication processing unit    -   143, 243, 520, 620 second communication processing unit    -   300,700 terminal apparatus    -   331.710 reception processing unit    -   333,720 transmission processing unit

What is claimed is:
 1. A method of a terminal apparatus configured tocommunicate with a first base station comprising: performingmeasurements of signals transmitted by a second base station using atleast one beam; transmitting, to the first base station, firstinformation indicating results of the measurements; receiving a RRCmessage relating to RRC Reconfiguration the first base station, the RRCmessage relating to RRC Reconfiguration including second informationrelated to a beam; the RRC message relating to RRC Reconfiguration onmessage being a message transmitted to the terminal apparatus by thefirst base station, the RRC message relating to RRC Reconfigurationincluded in a HANDOVER REQUEST ACKNOWLEDGE message that is transmittedfrom the second base station to the first base station in response to aHANDOVER REQUEST message including the first information after theHANDOVER REQUEST message is transmitted from the first base station tothe second base station; and transmitting, to the second base station, arandom access preamble signal based on the second information.
 2. Themethod according to claim 1, wherein the first information includesindex information indicating the beam and information related to qualityof the beam.
 3. The method according to claim 1, further comprising:receiving, from the first base station, information related to thenumber of beams transmitted by the second base station.
 4. The methodaccording to claim 1, wherein the RRC message relating to RRCReconfiguration includes resource information indicating a radioresource for transmitting the random access preamble signal.
 5. Themethod according to claim 4, wherein the resource information isinformation to be transferred from the first base station to theterminal apparatus.
 6. The method according to claim 4, furthercomprising: receiving, from the first base station, retransmission cycleinformation indicating a retransmission cycle of the random accesspreamble signal, with the resource information.
 7. The method accordingto claim 1, wherein the measurements includes measurements of referencesignals transmitted using a plurality of beams.
 8. The method accordingto claim 1, wherein the second information is information related to oneof a plurality of beams.
 9. A method of a first base station configuredto communicate with a terminal apparatus comprising: receiving, from theterminal apparatus, first information indicating results ofmeasurements, the measurements performed by the terminal apparatus andthe results of the measurements indicating results of measurements ofsignals transmitted by a second base station using at least one beam;transmitting a RRC message relating to RRC Reconfiguration message tothe terminal apparatus, the RRC message relating to RRC Reconfigurationmessage including second information related to a beam; wherein the RRCmessage relating to RRC Reconfiguration message is included in aHANDOVER REQUEST ACKNOWLEDGE message that is transmitted from the secondbase station to the first base station in response to a HANDOVER REQUESTmessage including the first information after the HANDOVER REQUESTmessage is transmitted from the first base station to the second basestation; and wherein the terminal apparatus transmits, to the secondbase station, a random access preamble signal based on the secondinformation.
 10. A method of a second base station configured tocommunicate with a terminal apparatus comprising: transmitting signalsto the terminal apparatus using at least one beam; receiving, from afirst base station, a HANDOVER REQUEST message including firstinformation indicating results of measurements, the measurementsperformed by the terminal apparatus and the results of the measurementsindicating results of measurements of signals transmitted by a secondbase station using at least one beam; transmitting, to the first basestation, a HANDOVER REQUEST ACKNOWLEDGE message including a RRC messagerelating to RRC Reconfiguration message in response to the HANDOVERREQUEST message, the RRC message relating to RRC Reconfiguration messageincluding second information related to a beam and the RRC messagerelating to RRC Reconfiguration message transmitted to the terminalapparatus from the first base station; and wherein the terminalapparatus transmits, to the second base station, a random accesspreamble signal based on the second information.